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Objective: We explored the use of ultrasonography in determining the minimal transverse diameter of the subglottic airway (MTDSA) for the purpose of choosing an appropriate model of reinforced cuffed endotracheal tube. Methods: A total of 110 pediatric patients who received general anesthesia and tracheal intubation for selective surgeries at the hospital from February 2019 to February 2022 were chosen. They were then randomly assigned to three groups: 39 in the MTDSA group, 35 in the age formula group, and 36 in the height formula group. We assessed how accurately the appropriate endotracheal tube model was predicted in each group and compared their predictive performance. Results: The age range of the enrolled pediatric patients was 3–6 years old. The ultrasonic measurement method demonstrated a prediction accuracy of 87.18%, while the age formula method and height formula method exhibited lower accuracy rates of 54.29% and 47.22%, respectively. Notably, the ultrasonic measurement method outperformed the other two methods significantly (P < 0.05). In the MTDSA group, 2 patients had their catheters changed during anesthesia, and the proportion of patients who changed their catheters was 5.13%. In the MTDSA group, 6 catheters were replaced, and the frequency of catheter replacement was 15.38%. In contrast, these percentages were much higher in the age formula group, at 31.43% and 45.71%, and in the height formula group, at 36.11% and 52.78%. The latter two groups had significantly higher values than the MTDSA group (P < 0.05). Regarding complications such as hoarseness, laryngeal edema, aspiration, and laryngospasm, the MTDSA group experienced a notably lower total incidence of 7.69% compared to the 37.14% in the age formula group and 41.67% in the height formula group, demonstrating statistical significance (P < 0.05). Conclusion: The ultrasonic measurement technique employed in MTDSA exhibits impressive precision when it comes to forecasting the specific model of a reinforced cuffed endotracheal tube for pediatric patients. This enhanced accuracy contributes significantly to minimizing the need for tube replacements during anesthesia and the associated complications. It holds immense importance in assisting clinicians in selecting the most appropriate pediatric endotracheal tube model for anesthesia induction. [ABSTRACT FROM AUTHOR]

Body-wave speeds and polarization directions in a homogeneous and isotropic medium can be influenced by the presence of an initial deviatoric stress, which is conventionally ignored in seismic-wave propagation theories. To the first order, the P -wave speed is sensitive to the initial deviatoric stress, and the P -wave polarization has a perturbation perpendicular to the propagation direction. In addition, the S waves travel at two distinct speeds, and the S -wave polarizations are in two orthogonal directions, which are constrained by the initial deviatoric stress and involve a perturbation parallel to the propagation direction. Using a subduction zone setting with an initial deviatoric stress on the order of tens of MPa, the P -wave speed perturbation, S -wave splitting time and polarization perturbation are estimated to be on the order of 0.01 per cent, 0.01 s and 0.01 per cent, respectively. While these effects are too small to be reliably resolved using seismic observations, the theory presented in this paper could be useful for ultrasonic stress measurements in engineering applications. [ABSTRACT FROM AUTHOR]

Incidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply. [ABSTRACT FROM AUTHOR]

Introduction: Non Carious Cervical Lesions (NCCLs) represent a prevalent dental condition characterised by the erosion of tooth structure at the cementoenamel junction without the involvement of dental caries. These lesions pose significant challenges due to their aesthetic impact, potential for dentinal hypersensitivity, plaque accumulation, pulpal complications and compromised structural integrity of the teeth. Tooth preparation traditionally uses diamond abrasive points and tungsten carbide burs for micromechanical adhesion. Newer methods, like ultrasonic tips, offer a more conservative approach, but limited research has compared their effects on bond strength, particularly in cervical cavity restorations with nanohybrid composites. Aim: To compare the surface roughness of cervical cavity preparations utilising diamond abrasive points and ultrasonic tips, and to evaluate the shear bond strength of restorations with composite resin. Materials and Methods: The present in-vitro comparative study was conducted in the Department of Conservative Dentistry and Endodontics, Guru Nanak Institute of Dental Sciences and Research, Panihati, Kolkata, West Bengal, India, from October 2023 to December 2023. The study included 52 freshly extracted maxillary 1st premolar teeth extracted for orthodontic reasons. These teeth were divided into two groups: Group-I (n=26) underwent surface preparation using a diamond abrasive point (No. 835-012, Piranha, SS White, USA), while Group-II (n=26) was prepared using an ultrasonic tip (Woodpecker G 20, Guilin Woodpecker, China). Teeth were cleaned, disinfected and stored in 0.1% thymol solution before being prepared with diamond abrasive points or ultrasonic tips, following which the specimens were restored using nanohybrid composite material (Solare X, GC Corporation, Japan). Surface roughness was assessed using a digital profilometer before the restoration, and the shear bond strength of repaired specimens was measured with a Universal Testing Machine. Statistical analysis was performed using GraphPad Prism, with independent samples t-tests applied to compare results between groups, and a significance level set at 5%. Results: Group-I exhibited greater surface roughness (6.33±2.18 μm) compared to Group-II (4.91±1.57 μm). Group-I also showed higher shear bond strength (62±13 MPa) than Group-II (59.3±19.9 MPa), though this variation was not statistically significant (p-value=0.56). Conclusion: Within the present study's limitations, diamond abrasive points created significantly greater surface roughness compared to ultrasonic tips. However, no statistically significant variations have been observed in shear bond strength among the two methods, suggesting that ultrasonic tips may be considered as an alternative to diamond abrasive points in clinical settings, avoiding their drawbacks while achieving adequate restoration retention. [ABSTRACT FROM AUTHOR]

Lichens are a mutualistic symbiosis between a fungus and one or more photosynthetic partners. They are photosynthetically active during desiccation down to relative water contents (RWCs) as low as 30% (on dry mass). Experimental evidence suggests that during desiccation, the photobionts have a higher hydration level than the surrounding fungal pseudo-tissues. Explosive cavitation events in the hyphae might cause water movements towards the photobionts. This hypothesis was tested in two foliose lichens by measurements of ultrasonic acoustic emissions (UAEs), a method commonly used in vascular plants but never in lichens, and by measurements of PSII efficiency, water potential, and RWC. Thallus structural changes were characterized by low-temperature scanning electron microscopy. The thalli were silent between 380% and 30% RWCs, when explosive cavitation events should cause movements of liquid water. Nevertheless, the thalli emitted UAEs at ~5% RWC. Accordingly, the medullary hyphae were partially shrunken at ~15% RWC, whereas they were completely shrunken at <5% RWC. These results do not support the hypothesis of hyphal cavitation and suggest that the UAEs originate from structural changes at hyphal level. The shrinking of hyphae is proposed as an adaptation to avoid cell damage at very low RWCs. [ABSTRACT FROM AUTHOR]

Ultrasonic thickness measurement depends on the capability of the equipment and its operating characteristics, as well as on the auxiliary means used to adjust the system and analyse the obtained results. The characteristics of the ultrasonic device commonly used as a flaw detector are crucial for achieving accurate and precise results and are very important for the reliability of the results obtained in the measurement process, especially in production systems. This article aims to determine the quantitative variations in thickness caused by influencing parameters of the ultrasonic device and chosen ultrasonic probe, their quantification of interactions, and the significance of their influence on the accuracy and precision of the results. In the experimental part of the research, a factorial plan of the experiment was carried out to determine the influence of the ultrasonic device and the type of ultrasonic probe on the variability of the results of the ultrasonic thickness measurement. The parameters of the ultrasonic device and probes were analysed, and the experimental plan for developing the regression model was elaborated. The response surface methodology was applied, and the in-service measurement process was simulated using Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

The carbon steel pipe line of the dehydrogenation tail gas system in a certain styrene unit has a thinning rate of 55.51% and a corrosion rate of up to 5.29 mm/a after one year of use, which restricts the long-term stable operation of the plant. The corrosion of the dehydrogenation tail gas carbon steel pipeline was inspected through electromagnetic eddy current scanning, ultrasonic thickness measurement, and macroscopic inspection. The impact of corrosive medium, process operating parameters, on-site pipeline location and material on pipeline thinning in the dehydrogenation tail gas system was analyzed. The results indicate that the localized corrosion and thinning of the dehydrogenation tail gas carbon steel pipeline are caused by a combination of carbon dioxide corrosion and erosion corrosion under certain temperature and pressure. To alleviate corrosion issues, it is recommended to re-evaluate the process operating conditions of the dehydrogenation tail gas system, add cooling equipment before the dehydrogenation tail gas compressor, or upgrade the pipeline material to 304 austenitic stainless steel. Or consider adding corrosion inhibitors to the dehydrogenation exhaust system. At the same time, regular electromagnetic eddy current scanning or ultrasonic thickness measurement should be carried out to monitor the relevant pipelines and prevent leaks in a timely manner. [ABSTRACT FROM AUTHOR]

Experimental investigation of the elastic behaviours of lacustrine shales remains sparse, although they play an essential role in source rock evaluation, unconventional reservoir exploration and development, and the seal integrity evaluation for geological storage of CO2 and nuclear waste disposal. We make the ultrasonic velocity measurement of 63 organic‐rich shale samples (Chang 7, Qingshankou and Lucaogou formation) from three typical lacustrine basins in China. It is found that the P‐ and S‐wave velocity of Chang 7 and Qingshankou shale corresponding to the fresh‐brackish lacustrine depositional environment is mainly impacted by the clay and organic matter content, whereas their elastic anisotropic magnitude is mostly influenced by clay content. The P‐ and S‐wave velocities of Lucaogou shale corresponding to the saline lacustrine depositional environment are mainly affected by the total organic carbon and porosity and exhibit weak anisotropy linked to organic matter enrichment. Exponential law well captures the relationship between anisotropic magnitude and velocity perpendicular to bedding for both saline and fresh‐brackish water lacustrine shales, although there exists notable discrepancy, particularly at low velocities. The disparity in elasticity between laminations has a profound impact on the magnitude of elastic anisotropy and shapes the trend of velocity variations. [ABSTRACT FROM AUTHOR]

A multi-channel simultaneous emission non-invasive flow velocity measurement system is introduced and validated in this paper, which adapts to industrial large-diameter pipelines. In particular, the ultrasonic simultaneous emission mode is applied to the whole system to achieve real-time flow measurement. This technology reduces measurement errors in ultrasonic flow measurements caused by changes in fluid state and timing variations. Sixteen non-invasive ultrasonic transducers are used in the system, together with the precision measurement circuit, efficient data acquisition system and real-time display upper computer program. The flow rate can be accurately measured and displayed without interrupting the fluid flow. Furthermore, a period-invariant dual-threshold method is applied to locate feature points in the ultrasonic signals to ensure that high accuracy and stability are maintained in the final result. [ABSTRACT FROM AUTHOR]

In fermentation processes, changes in yeast cell count and substrate concentration are indicators of yeast performance. Therefore, monitoring the composition of the biological suspension, particularly the dispersed solid phase (i.e., yeast cells) and the continuous liquid phase (i.e., medium), is a prerequisite to ensure favorable process conditions. However, the available monitoring methods are often invasive or restricted by detection limits, sampling requirements, or susceptibility to masking effects from interfering signals. In contrast, ultrasound measurements are non-invasive and provide real-time data. In this study, the suitability to characterize the dispersed and the liquid phase of yeast suspensions with ultrasound was investigated. The ultrasound signals collected from three commercially available Saccharomyces yeast were evaluated and compared. For all three yeasts, the attenuation coefficient and speed of sound increased linearly with increasing yeast concentrations (0.0–1.0 wt%) and cell counts (R2 > 0.95). Further characterization of the dispersed phase revealed that cell diameter and volume density influence the attenuation of the ultrasound signal, whereas changes in the speed of sound were partially attributed to compositional variations in the liquid phase. This demonstrates the ability of ultrasound to monitor industrial fermentations and the feasibility of developing targeted control strategies. [ABSTRACT FROM AUTHOR]

Bearings play a key role in rolling mills, and the uniformity of their lubricant film directly affects the degree of wear of bearings and the safety of equipment. Due to long-term stress, the lubricant film inside the bearing is not uniformly distributed, resulting in uneven wear between the journal and the shaft tile, which increases the potential safety hazards in production. Traditional disassembly inspection methods are complex and time-consuming. Ultrasonic nondestructive testing technology, which has the advantages of nondestructive and adaptable, has become an effective means of assessing the thickness of the oil film in bearings. In this study, an experimental platform for calibrating the lubricant film thickness in bearings was constructed for the first time, and the acoustic characteristics of different thicknesses of the oil film were measured using ultrasonic detection equipment to verify the accuracy of the simulation process. The experimental results show that after discrete Fourier transform processing, the main features of the frequency channels of the reflected acoustic signals of different thicknesses of the oil film are consistent with the finite element simulation results, and the errors of the oil film thicknesses calculated from the reflection coefficients are within 10% of the set thicknesses, and the measurement ranges cover from 5 μm to 250 μm. Therefore, the above method can realize the accurate measurement of the thicknesses of the oil film in bearings. [ABSTRACT FROM AUTHOR]

Microwave-absorbing suspicious objects (MASOs) found using microwave-induced thermoacoustic imaging (MTI) can be divided into two types—endogenous (such as tumors or hematoceles) and exogenous (such as calculi or foreign bodies). These have different microwave absorption or ultrasonic velocity than normal human tissue, so MTI is efficient in detecting these anomalies. However, the existing MTI techniques can only reflect morphological information, making it difficult to distinguish the type of each anomaly. In this paper, a newly enhanced MTI system composed of a multiple-element ring transducer and a parallel data acquisition system (DAS) is presented. By using ultrasonic velocity and microwave absorption measurements, where the ultrasonic velocity is mainly used as an additional parameter to reflect mechanical characteristics, the type of the detected anomaly can be identified. In our experiments, the MASO can be located through the absorption difference detected by MTI. Due to the use of multiple-element transducers and a parallel DAS, the raw data can be acquired within about 20 ms for a two-dimensional image. Additionally, the ultrasonic velocity of the MASO can be calculated from the time sequence diagram of ultrasound propagation with a maximum time error of 0.084 μs. Apart from distinguishing the type of the anomaly, the proposed ultrasonic velocity-assisted microwave-induced thermoacoustic imaging (US-MTI) system has other advantages, such as being noninvasive, and allowing rapid imaging and a large field of view, which make US-MTI a suitable modality for regular screening. [ABSTRACT FROM AUTHOR]

Abstract Incidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply.

In order to grasp the actual state and change of the point defects on the aluminum pool bottom of 49-2 swimming pool reactor (49-2 reactor for short), to further provide data support for the service performance evaluation, and to ensure the safe and stable operation, a water immersion ultrasonic measurement system was developed according to the information of the pool bottom structure, the media in the pool, and the pool wall materials. The distribution of point defects at the bottom of the pool is examined comprehensively, and the point defect depth is accurately measured. The water immersion ultrasonic measurement equipment integrates a water immersion ultrasonic transmitter, a multi-axis scanning device and a controllable underwater floating robot. It uses ultrasonic waves to scan uneven areas such as pits on the surface of the aluminum plate. Due to changes in the surface properties of the material being tested, the sound path of the echo reflected from the ultrasonic interface changes, and the depth of the pit is obtained by measuring the difference in the sound path of the echo sound beam on the intact surface and the bottom of the pit. Before the on-site measurement, a 15 MHz water immersion point focusing probe was used to scan the pit simulation test block. At the same time, a laser confocal microscope (8.0 μm step diameter) was used to measure the pit simulation test block. The scan data were compared and analyzed to determine Measurement accuracy was confirmed. In the actual inspection, the remote carrier device, that is, the underwater floating robot is used to move the scanning device to the inspection area, grid lines are used for grid scanning, and signal collection and analysis are completed through a multi-channel ultrasonic instrument. Finally, the accelerated corrosion experiment simulation analysis results were used, combined with the maximum point defect depth data measured in this study for comparative analysis, and the time-limited aging analysis conclusion of the 49-2 reactor bottom material was given. This study is the first time to conduct remote underwater nondestructive testing of the actual state of the defects at the bottom of the pool in 49-2 reactor. Compared with the historical data, the distribution of the defects at the bottom of the pool is basically consistent with the measured data of the pit depth, and the maximum pit depth is 1.495 mm. The research conclusion provides important data support for time-limited aging analysis of materials at the bottom of 49-2 reactor pool, and the underwater ultrasonic measurement technology developed can also be applied to aging management and service life analysis and demonstration of the same type of pool reactor vessels and spent fuel storage pools.

The elastic properties and wave propagation of porous rocks are sensitive to the stress variation. The existing theories mainly focus on the impacts of effective stress, confining and pore pressures. The physics of uniaxial stress effect on rock elasticity and wave propagation is seldom well studied, although the uniaxial stress case is frequently encountered in several scenarios, such as the laboratory loading and the subsurface tectonic deformation. Therefore, we propose a new dual‐porosity model to describe the effect of uniaxial effective stress on elastic properties of dry porous rocks, based on the Palmer equation and Shapiro dual‐porosity model. The Gurevich squirt‐flow model is then incorporated to model the dispersion and attenuation of wave velocities of fluid‐saturated porous rocks. Modelling results show that the increase of uniaxial effective stress inflates the P‐ and S‐wave velocities along the stress direction until the velocities asymptotically reach their maximum values within the elastic limit. However, the relevant wave dispersion and attenuation gradually decline with the elevating stress possibly due to the gradual closure of cracks. The effect of viscosity, fluid modulus and crack aspect ratio on wave dispersion is investigated in detail as well. By comparing our model to the published laboratory ultrasonic measurements, we confirm the validity of our model. Furthermore, our dual‐porosity model is used to establish a rock‐physics approach to estimate the wave velocities with the well‐logging data. The well‐logging examples show the reasonable agreement between the predicted results and real data, illustrating the feasibility of our approach. [ABSTRACT FROM AUTHOR]

In high-precision ultrasonic measurement systems, diffraction correction models accounting for electrical and mechanical boundary conditions may be needed, as shown in prior work using a finite element diffraction correction (FEDC) model for one-way transmit-receive systems. Such descriptions may also be needed for pulse-echo and multiple-reflection ultrasonic measurement applications. The FEDC model is here generalized to n -way measurement systems (n = 1, 2, 3,...) using coaxially aligned piezoelectric transducers in a fluid medium. Comparisons are made with existing diffraction correction models, based on baffled-piston theory combined with (i) specular reflection or (ii) reflection modeled as radiation from a "new source." Numerical results are given for an example system with two identical cylindrical piezoelectric disks, operating in a fluid medium at ambient conditions. The piston-type diffraction correction models deviate notably from the FEDC model both in the near- and far-fields, and also from each other. The deviations are expected to be application-specific and depend, e.g., on the reflector-to-sound-beam diameter ratio, distance, frequency, and the transducers' vibration patterns. The results show that accurate description of the diffraction effects, such as the one provided by the FEDC model, may be needed in high-precision ultrasonic measurement systems. [ABSTRACT FROM AUTHOR]

This article presents an overall examination of how small temperature fluctuations affect P-wave velocity (Vp) measurements and their uncertainties in concrete using embedded piezoelectric transducers. This study highlights the fabrication of custom transducers tailored for long-term concrete monitoring. Accurate and reliable estimation of ultrasonic wave velocities is challenging, since they can be impacted by multiple experimental and environmental factors. In this work, a reliable methodology incorporating correction models is introduced for the quantification of uncertainties in ultrasonic absolute and relative velocity measurements. The study identifies significant influence quantities and suggests uncertainty estimation laws, enhancing measurement accuracy. Determining the onset time of the signal is very time-consuming if the onset is picked manually. After testing various methods to pinpoint the onset time, we selected the Akaike Information Criterion (AIC) due to its ability to produce sufficiently reliable results. Then, signal correlation was used to determine the influence of temperature (20 °C to 40 °C) on Vp in different concrete samples. This technique proved effective in evaluating velocity changes, revealing a persistent velocity decrease with temperature increases for various concrete compositions. The study demonstrated the capability of ultrasonic measurements to detect small variations in the state of concrete under the influence of environmental variables like temperature, underlining the importance of incorporating all influencing factors. [ABSTRACT FROM AUTHOR]

Experimental results are presented for the contact acoustic nonlinearity of interfaces between two solid surfaces in dry contact which experience a moderate level of plastic deformation. The current research aims at investigating the effects of the elastoplastic hysteresis, surface roughness, and possible adhesive force on the acoustic nonlinearity. The ultrasonic results are compared with results from the elastoplastic contact model of Kim and Lee (2007) and the clapping model of Blanloeuil et al. (2020), which reveals that the nonlinearities are dominated by clapping of lightly contacting cracks at the interface at low pressures and by the elastoplastic nonlinear spring at high pressures. On top of this major trends, there are consistent minor trends which are attributed to the effects of adhesive force. There is a critical pressure level at which the adhesive clapping of cracks starts being more pronounced. As predicted by the model, the nonlinearity increases with the surface roughness and thus is always lower during unloading in the high pressure regime. The effects of the adhesion are investigated by measuring the nonlinearity at two different relative humidity levels. Some systematic, physically reasonable trends in the experimental results illustrates possible effects of the adhesive force on the acoustic nonlinearity. [ABSTRACT FROM AUTHOR]

Objectives: To develop a robust algorithm for estimating ultrasonic axial transmission velocity from neonatal tibial bone, and to investigate the relationships between ultrasound velocity and neonatal anthropometric measurements as well as clinical biochemical markers of skeletal health. Methods: This study presents an unsupervised learning approach for the automatic detection of first arrival time and estimation of ultrasonic velocity from axial transmission waveforms, which potentially indicates bone quality. The proposed method combines the ReliefF algorithm and fuzzy C‐means clustering. It was first validated using an in vitro dataset measured from a Sawbones phantom. It was subsequently applied on in vivo signals collected from 40 infants, comprising 21 males and 19 females. The extracted neonatal ultrasonic velocity was subjected to statistical analysis to explore correlations with the infants' anthropometric features and biochemical indicators. Results: The results of in vivo data analysis revealed significant correlations between the extracted ultrasonic velocity and the neonatal anthropometric measurements and biochemical markers. The velocity of first arrival signals showed good associations with body weight (ρ = 0.583, P value <.001), body length (ρ = 0.583, P value <.001), and gestational age (ρ = 0.557, P value <.001). Conclusion: These findings suggest that fuzzy C‐means clustering is highly effective in extracting ultrasonic propagating velocity in bone and reliably applicable in in vivo measurement. This work is a preliminary study that holds promise in advancing the development of a standardized ultrasonic tool for assessing neonatal bone health. Such advancements are crucial in the accurate diagnosis of bone growth disorders. [ABSTRACT FROM AUTHOR]

Single crystal elastic constants are vital parameters associated with the mechanical properties of polycrystals. To accurately invert these constants, precise experimental techniques must be employed. However, traditional ultrasonic measurement methods can introduce errors when dealing with complex microstructures. To address this issue, we propose an approach that combines metallographic measurements, homogenization techniques, and intelligent algorithms to invert the single crystal elastic constants of polycrystals. First, we developed a modified single scattering response (SSR) model based on metallographic measurements and the best-fitted spatial correlation function (SCF). In addition, different homogenization techniques were compared to enhance the accuracy of the model. We then propose an Adaptive Probability Differential Evolution Quantum Particle Swarm Optimization (AP-DE-QPSO) algorithm to enhance the accuracy of optimization results with an adaptive probability (AP) operator in the optimization process. After verification with three standard test functions, we demonstrated that the algorithm achieved higher accuracy. Finally, by utilizing the AP-DE-QPSO algorithm and fitting the spatial variance of the modified SSR model to the ultrasonic backscattering experimental data, we successfully inverted the global optimal solution of the single crystal elastic constants. The Self- Consistent averaging technique yielded the best results, with relative errors of approximately 3% for C11 and C44, and a relative error of approximately 10% for C12. Our study confirms the accuracy and reliability of the modified SSR model and AP-DE-QPSO algorithm in inverting the elastic constants of single crystals. [ABSTRACT FROM AUTHOR]

Ultrasonic thickness measurement of mechanical structures is one of the most popular and commonly used nondestructive methods for various kinds of process control and corrosion monitoring. With ultrasonic propagation speed being temperature-dependent, the thickness measurement can be performed reliably only when the thermal profile is completely known. Most conventional techniques assume the temperature of the test structure is uniform and at room temperature across its thickness. Such assumptions may lead to large errors in the thickness measurement, especially when there are significant temperature variations across the thickness. State-of-the-art techniques use external temperature measurements or implement iterative methods to compensate for the unknown thermal profiles. However, such techniques produce unsatisfactory results when the heat distribution is complex or varies rapidly with time. In this work, we propose a two-sensors technique, using both compressive and shear excitations, with a non-iterative rapid data processing method for accurate thickness measurement under arbitrary time-variant thermal profile. The independent behavior of shear and compressive waves is used to formulate a real-time thickness estimation technique. The developed technique is experimentally validated on a steel plate with fixed acoustic sensors. Test results show that the error in thickness estimation can be reduced by up to 98% compared to conventional thickness gauging methods. [ABSTRACT FROM AUTHOR]

The first section of this study is devoted to characterizing the lateral wave generated by a laser along the air-aluminum interface. This includes determining its propagation velocity, analyzing its spectrum, and evaluating the variation of its amplitude in relation to the generation/detection distance (d). The obtained results have shown that the lateral wave propagates at the speed of the longitudinal volume wave, following the d–n law, where n equals 2.46. Its spectrum exhibits a wide bandwidth, with a cutoff frequency of fc = 3 MHz. The second part of the paper focuses on utilizing these waves for surface defect detection, with a comparative analysis of results obtained with Rayleigh waves. Various tests were conducted to analyze the impact of defects on the lateral wave on transmitted or reflected modes. The outcomes illustrate modifications in the temporal signals and frequency spectra of the lateral wave in the presence of defects. [ABSTRACT FROM AUTHOR]

The accuracy of ultrasonic nondestructive examination is limited by the limitation of near field diffraction. With the development of nearfield optical, angular spectrum method is introduced into the acoustic field, which provides a significant direction for the ultrasonic diffraction limit resolution detection. The main research of this paper is the transmission of near field ultrasound in thin workpiece and the law of the interaction of tiny flaws. The paper establishes the relationship between the longitudinal wave signal and the structure of the workpiece and the types of flaws. A method is found that whether there are flaws can be determined near field area by analysing the acoustic field characteristics of workpiece surface. Finally, comparing the calculation results with the finite element simulation, they verify each other, the method turns out to be correct in this paper. The model can also be used to improve the ultrasonic noise reduction algorithm and the extraction of minimal defect feature. It has a greatly practical significance. [ABSTRACT FROM AUTHOR]

We present an analysis of a three-layered structure used for both launching and detecting picosecond acoustic waves. To enhance the optical sensitivity to the acoustic disturbances, a cavity is designed, which acts as a Fabry–Perot interferometer. We use analytic modeling based on dual optical and acoustic transfer matrix formalism to analyze the coupled optical and acoustic wave propagation. Assuming a three-layer transducer made of an optical cavity sandwiched between two thin metallic layers, the model allows for mastering of the coupled optical and acoustic responses, which leads to an optimum design of the structure, and it highlights the various acoustic contributions to the reflectivity changes. The sensitivity of this three-layered structure to acoustic disturbances is compared to the numerical predictions we performed for the standard opto-acoustic transducer made of a single metallic layer. [ABSTRACT FROM AUTHOR]

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This study investigates the application of artificial intelligence (AI) to predict the compressive strength of self-compacting concrete (SCC) through ultrasonic measurements, thereby contributing to sustainable construction practices. By leveraging advancements in computational techniques, specifically artificial neural networks (ANNs), we developed highly accurate predictive models to forecast the compressive strength of SCC based on ultrasonic pulse velocity (UPV) measurements. Our findings demonstrate a clear correlation between higher UPV readings and improved concrete quality, despite the general trend of decreased compressive strength with increased air-entraining admixture (AEA) concentrations. The ANN models show exceptional effectiveness in predicting compressive strength, with a correlation coefficient (R2) of 0.99 between predicted and actual values, providing a robust tool for optimizing SCC mix designs and ensuring quality control. This AI-driven approach enhances sustainability by improving material efficiency and significantly reducing the need for traditional destructive testing methods, thus offering a rapid, reliable, and non-destructive alternative for assessing concrete properties. [ABSTRACT FROM AUTHOR]

Given the growing importance of organic-rich shale as unconventional reservoirs, a thorough understanding of the elastic and anisotropic behavior of shales is of great concern. However, for lacustrine shales, the complex lithofacies assemblage with geological deposition makes it challenging. Four lithofacies (argillaceous, mixed, siliceous, and calcareous) are recognized for 40 lacustrine shale samples from Jurassic formation in Sichuan Basin on the basis of their mineral compositions. We perform ultrasonic velocity measurements on 40 pairs of shale plugs at varied confining pressures, attempting to uncover the controls on the anisotropic properties of different lithofacies. The experimental results reveal that the total porosity, clay, and organic matter would positively contribute to velocity anisotropy of Jurassic shales. Combined with microstructure and pressure-dependent velocity analysis, the preferred orientations of platy clay particles and lenticular kerogen, the development of clay pores along clay fabric, and the sub-parallel micro-cracks induced by hydrocarbon expulsion are treated to be the controlling mechanisms. We add the total porosity, clay content, and kerogen volume together, intending to distinguish the elastic and anisotropic properties of four lithofacies. Generally, argillaceous shales, the dominant lithofacies in Jurassic formation, could be characterized by the highest clay and total organic content (TOC), the lowest bedding-normal velocities, and the strongest velocity anisotropy. Finally, with the laboratory data, two rock-physics-driven exponential relationships are proposed to predict the P- and S-wave velocity anisotropy with the bedding-normal velocities. [ABSTRACT FROM AUTHOR]

This work explores experimentally the effects of DC electrical currents on lubricant film thickness alteration in lubricated sliding steel contacts in the boundary and mixed regime as measured by ultrasound. The experiments were performed in a two-electrode cell-based pin-on-disk tester instrumented with ultrasonic transducers. Unelectrified and electrified tribological tests were conducted on steel flat-on-flat contacts under various speeds and loads using both a mineral base oil and a gear oil. Film thickness, coefficient of friction (CoF), and electrical contact resistance (ECR) were measured during short experiments (30 s) in unelectrified and electrified (1.5 and 3 A) conditions. The results suggest that film thickness, CoF, and all ECR are altered by passing DC currents through the contact. In particular, film thickness increased and decreased, respectively, by applying electricity at the different speeds and loads tested. These alterations were majorly ascribed to oil viscosity decrease by local heat and surface oxidation caused by electrical discharge and break down at the interface. [ABSTRACT FROM AUTHOR]

There exist issues of ill-adaptability and low-accuracy in ultrasonic bolt stress measurement based on acoustic elasticity and scattering attenuation. Therefore, a bolt axial stress measurement method based on ultrasound multi-feature fusion is proposed in this paper. Firstly, ultrasound characteristic parameters based on the theory of acoustic elasticity are extracted, including the difference of time-of-flight (TOF) and the longitudinal wave attenuation coefficient in polycrystalline materials within the Rayleigh scattering range. Then, following the dimension reduction principle, the difference of TOF, attenuation coefficient, and clamping length are chosen as the input feature vectors for the fusion model. Subsequently, the SVR model is employed to establish a multi-feature fusion model for bolt axial stress measurement. Calibration and measurement experiments are conducted using the constructed experimental platform. Comparative analysis between the traditional measurement methods and the proposed method reveals that the SVR model can adapt to measurements of bolts with different lengths, overcoming the limitations of traditional methods. Furthermore, the measurement results of different fusion algorithms show that SVR yields significantly lower average relative errors in the measurement of the three bolts (3.35%, 4.44%, and 4.48%) compared to BP and RBF algorithms. This indicates higher measurement accuracy and immunity to low-stress effects. [ABSTRACT FROM AUTHOR]

The relationship between acoustic parameters and the microstructure of a Cu30Zn brass plate subjected to plastic deformation was evaluated. The plate, previously annealed at 550 °C for 30 min, was cold rolled to reductions ranging from 10% to 70%. Linear ultrasonic measurements were performed on each of the nine specimens, corresponding to the nine different reductions, using the pulse-echo method to record the times of flight of longitudinal waves along the thickness axis. Subsequently, acoustic measurements were conducted to determine the nonlinear parameter β through second harmonic generation. Microstructural analysis, carried out by X-ray diffraction, Vickers hardness testing, and optical microscopy, revealed an increase in deformation twins, reaching a maximum at 40% thickness reduction. At higher deformations, the microstructure showed the generation and proliferation of shear bands, coinciding with a decrease in the twinning structure and an increase in dislocation density. The longitudinal wave velocity exhibited a 0.9% decrease at 20% deformation, attributed to dislocations and initial twin formation, followed by a continuous increase up to 2% beyond this point, resulting from the combined effects of twinning and shear banding. The nonlinear parameter β displayed a notable maximum, approximately one order of magnitude greater than its original value, at 40% deformation. This peak correlates with a roughly tenfold increase in twinning fault probability at the same deformation level. [ABSTRACT FROM AUTHOR]

In this study, the focus is on investigating prevalent issues of rupture and wrinkling that occur during the extra-deep drawing process. These defects are very common in a local sanitary equipment industrial company, mainly in the manufacture of bathtubs, which increases scrap and leads to loss of time and costs in production. To analyze these defects, a numerical simulation of the bathtub extra-deep drawing process was performed with industrial parameters. The originality lies in controlling non-uniform blank holder pressures generated from six actuators in order to control the flow of the blank between the blank holder and the die and ensure the production of defect-free bathtubs. 3D and ultrasonic thickness measurements were performed on a bathtub manufactured without defects. Numerical and experimental plots of the thickness reduction show that the two approaches are in good agreement. The numerical results demonstrate that there are no rupture or wrinkling defects in the bathtub final shape, which exactly matches the actual case manufactured by the company. The numerical analysis was also performed on different cases that can cause rupture and wrinkling defects, namely: the influence of the blank holder pressure, the blank initial shape, and the die design using draw beads. [ABSTRACT FROM AUTHOR]

In the resolution of the large divergence between pressure calculated by way of axial stress components from elastic constants and pressure determined by an equation of state, a 2nd order pressure dependency of elastic constants is introduced. Incorporating results from the equation of state and ultrasonic measurements in the literature, we determined the pressure dependency of x-ray elastic constants of gold and established functions for the calculation of macro-stress components from its macro-strain counterparts. The precision of stress components through these functions is estimated to be at 1% level. The determination of stress components, including crucial shear components, through analysis of an x-ray diffraction image, is demonstrated. [ABSTRACT FROM AUTHOR]

This paper introduces a reliable laser ultrasonic technique without damage to the surface in the thermoelastic regime that provides a one-side access method for simultaneously determining the thickness and ultrasonic wave velocity by employing multiple wave modes. Initially, this study determines the optimal separated distance between two laser beams to achieve an effective signal-to-noise ratio of the employed wave modes. Subsequently, a pre-established ratio of 0.95 for the velocity of skimming longitudinal waves and longitudinal waves enables the simultaneous calculation using a combination of the skimming longitudinal wave, reflected shear wave, and mode-converted longitudinal wave in a single measurement. Experiments were carried out on various plane plates made of aluminium alloy 6061, ranging in thickness from 4 to 20 mm, demonstrating a high accuracy in thickness measurement, with a maximum absolute error of 0.05 mm. Compare the results of ultrasonic wave velocity measurements with theoretical calculations, the maximum absolute error is 32 m/s and 80 m/s for longitudinal wave and shear wave, respectively. [ABSTRACT FROM AUTHOR]

The surface density of nonporous membranes is estimated with a conventional ultrasonic immersion measurement system without need for a priori information about the membrane such as wave speed, density, thickness or impedance under most testing conditions. The derivation, theoretical limitations and practical restrictions of the technique are discussed. The broadband nature of the measurement allows the surface density values to be estimated at multiple discrete frequencies within the useful bandwidth of the transducer. In experimentation, the technique was used to measure surface densities in a range of 0.044–0.328 kg/m2. All calculated surface densities are within 5% or less of their nominal values with an average percent difference of 1.7%. [ABSTRACT FROM AUTHOR]

Canopy height serves as an important dynamic indicator of crop growth in the decision-making process of field management. Compared with other commonly used canopy height measurement techniques, ultrasonic sensors are inexpensive and can be exposed in fields for long periods of time to obtain easy-to-process data. However, the acoustic wave characteristics and crop canopy structure affect the measurement accuracy. To improve the ultrasonic sensor measurement accuracy, a four-year (2018-2021) field experiment was conducted on maize and wheat, and a measurement platform was developed. A series of single-factor experiments were conducted toinvestigate the significant factors affectingmeasurements, including the observation angle (0-60°), observation height (0.5-2.5 m), observation period (8:00 -18:00), platform moving speed with respect to the crop (0-2.0 m min-1), planting density (0.2-1 time of standard planting density), and growth stage (maize from three -leaf to harvest period and wheat from regreening to maturity period). The results indicated that both the observation angle and planting density significantly affected the results of ultrasonic measurements (p-value< 0.05), whereas the effects of other factors on measurement accuracy were negligible (p-value > 0.05). Moreover, a double-input factor calibrationmodelwasconstructed to assess canopy heightunder different years by utilizing the normalized difference vegetation index and ultrasonic measurements. The model was developed by employing the least-squares method, and ultrasonic measurement accuracy was significantly improved when integrating themeasured value of canopy heights and the normalized difference vegetation index (NDVI). The maize measurement accuracy had a root mean squared error (RMSE) ranging from 81.4 mm to 93.6 mm, while the wheat measurement accuracy had an RMSE from 37.1mmto 47.2mm. The research results effectively combine stable and low-cost commercial sensors with ground-based agricultural machinery platforms, enabling efficient and non-destructive acquisition of crop height information. [ABSTRACT FROM AUTHOR]

This work provides the description of an experimental study for assessing the hardness of metallic test samples, subjected to the Jominy End-Quench Hardenability Test, by employing typical microhardness tests. Additionally, experimental measurements of the propagation velocity of ultrasound in the test samples were correlated with the microhardness results. A systematic protocol is presented for undergraduate mechanical engineering lectures, addressing the development of experiments, including the sorting and analysis of the resulting data; also, its impact on the expected competencies and abilities of the students is discussed. Several test samples of AISI 4140 steel were used for three experimental sets: heat-treated with the Jominy End-Quench Hardenability Test, fully tempered, and non-treated samples. All samples were evaluated by using typical microhardness tests and ultrasonic pulse-echo measurements to quantify their hardness at multiple locations. The proposed methodology not only strengthened some of the different required abilities of engineering students but also introduces a new procedure, using ultrasonic signals, to estimate hardness in undergraduate programs. The obtained results show a significant correlation between the experimental data from microhardness and ultrasonic measurements, with a maximum precision of -96.36% (inverse correlation) within the studied range. A discussion is provided regarding the means of improving the skills of undergraduate students in the course of Material Science, including experimental mechanical testing abilities through these systematic methods. [ABSTRACT FROM AUTHOR]

Introduction: Ulnar nerve enlargement is observed in ultrasound (USG) in patients with cubital tunnel syndrome (CuTS). This study aims to compare the ultrasound size of the ulnar nerve between CuTS patients and control subjects, to find the cut off size for diagnosis, and to validate the use of USG as an adjunct in CuTS diagnosis. Materials and Methods: There were 23 elbows with clinical and nerve conduction test (NCT) confirmed CuTS, and 42 elbows in the control group. Cases with elbow deformities, old ulnar nerve injuries and postoperative cases were excluded. The ulnar nerve cross sectional area (CSA) was measured at 6 different levels and positions: over the medial epicondyle (ME) in elbow flexion/extension, 2 cm and 5 cm distal to the ME, 2 cm and 5 cm proximal to the ME. A cut off CSA value for CuTS diagnosis was derived. Correlation between ulnar nerve CSAs and NCT was analysed. Results: The age and gender distribution were similar in both groups (61.2 vs 56.6; M > F, p > 0.05). The mean CSA of the CuTS group vs control group was 19.2 mm2 vs 7.0 mm2, 19.5 mm2 vs 7.1 mm2, 20.8 mm2 vs 8.1 mm2 at ME flexion, ME extension and maximal CSA respectively. The derived CSA cut off value for CuTS at ME flexion, ME extension and maximal CSA were 10.5 mm2, 11.5 mm2, and 15 mm2 respectively. The CSA difference at different levels between the 2 groups were significant except at 5 cm proximal to ME. A strong negative correlation was seen between the CSA and the across elbow nerve conduction velocity, with correlation coefficient of −0.748 at ME flexion, −0.654 at ME extension and -0.676 at maximal CSA. Conclusion: USG can be used as an adjunct for the diagnosis of CuTS with high accuracy and patient safety. It can also be used to delineate possible anatomical etiologies at the cubital tunnel. [ABSTRACT FROM AUTHOR]

Abrasion occurs on the concrete surfaces of irrigation canals because of the flow of water and sand. Abrasion increases the roughness of the concrete surface. Increased roughness reduces water flow function. Underwater ultrasonic roughness measurements estimate roughness from the peak-to-peak strength of reflected underwater ultrasonic waves. However, the effect of turbid water flowing in a canal on peak-to-peak strength has been unclear. The objective of this study was to evaluate the effect of turbid water on underwater ultrasonic roughness measurements. The characteristics of the attenuation of the peak-to-peak strength of underwater ultrasonic waves were investigated as a function of the particle size and concentration of suspended solids. The suspended solids used in the experiments were kaolin with a particle size of 0.5 µm and alumina with particle sizes of 2, 4, and 8 µm. Peak-to-peak strength was measured as a function of the concentration of each particle size. The experimental results indicated that peak-to-peak strength was attenuated only with increasing concentrations of suspended solids and was not affected by particle size. A proposed correction equation for peak-to-peak strength took into consideration the concentration of suspended solids in turbid water. The coefficient of determination R2 between this equation and measured data was as high as 0.98. Using this correction equation, peak-to-peak strength without turbidity could be calculated from peak-to-peak strength measured in turbid water. It is thus possible to make effective use of underwater ultrasonic roughness measurements in turbid water. [ABSTRACT FROM AUTHOR]

Purpose: The main objective of this study was to investigate the efficacy of S-PRG filler-containing gel application in promoting dentin remineralization using ultrasonic velocimetry. Methods: Root dentin slabs of bovine teeth were sliced and formed into rectangles, treated with 0.1 M lactate buffer (pH 4.75) for 10 min, and then immersed in artificial saliva (pH 7.0). This treatment was repeated three times a day for 28 days. S-PRG filler-containing gel (PRG) and high-fluorine concentration silver diamine fluoride (SDF) solution were used. The treatment methods were: 1) untreated group, 2) PRG one-off application group, 3) SDF oneoff application group, 4) PRG frequent-time application group, and 5) SDF frequent-time application group. After treatment, dentin slabs were soaked in 0.1 M lactate buffer solution and dipped in artificial saliva. This treatment was repeated 3 times a day for 28 days. Results: The ultrasonic velocity of the untreated samples decreased slightly during the experimental period. In the one-off application group, ultrasonic velocities of SDF and PRG increased rapidly on day 7 and then decreased slightly during the experimental period. In the frequent-time application group, ultrasonic velocities of SDF and PRG increased during the experimental period; specimens treated with SDF had significantly higher ultrasonic velocities on each measurement day compared to specimens treated with PRG. Conclusion: From the results of this experiment, it was concluded that the S-PRG filler-containing gel and silver diamine fluoride solution appear to promote remineralization and inhibit dentin demineralization. [ABSTRACT FROM AUTHOR]

Coaxial rotor helicopters have great potential in civilian and commercial uses, with many advantages, but challenges remain in the accurate measurement of rotor blades' distance to prevent blade collision. In this paper, a blade tip distance measurement method based on ultrasonic measurement window and phase triggering is proposed, and the triggering time of the transmitter is studied. Due to the complexity of the measured signal, bandpass filtering and a time-of-flight (TOF) estimation based on the power density of the received signal are utilised. The method is tested on an experimental test platform with a pair of 200 kHz ultrasonic transducers. The experimental results show that the maximum ranging error is less than 1.0% for the blade tip distance in a range of 100–1000 mm. Compared with the amplitude threshold method, the proposed TOF estimation method works well on the received signal with a low SNR and improves the ranging accuracy by about 5 mm when the blade tip distance is larger than 500 mm. This study provides a good reference for the accurate measurement of rotor blade tip distance, and gives a solution for ranging high-speed rotating objects. [ABSTRACT FROM AUTHOR]

Accurate detection of the preload force of tower crane bolts is of great significance for the stable and safe operation of the equipment. The method of contact ultrasonic detection of bolt preload has always been the focus of attention, which can realize rapid in situ detection without damaging the parts. In order to improve the accuracy and convenience of ultrasonic measurement of bolt preload and meet the urgent needs of the actual industrial site for high-precision measurement of bolt preload, we propose to prepare ZnO piezoelectric coatings as functional layers for ultrasonic transducers using magnetron sputtering and deposit them directly on bolts. The growth behavior of the ZnO coatings is investigated by varying the sputtering power, sputtering gas pressure and target substrate distance, and the morphology, structure, and properties are characterized and analyzed. The ZnO piezoelectric coatings with high c-axis optimal growth orientation and excitation of ultrasonic longitudinal waves were finally obtained and verified to be effective and stable when applied to the bolts. [ABSTRACT FROM AUTHOR]

This study investigates the application of Ultrasonic Pulse Velocity (UPV) for crack depth estimation in cylindrical structures, focusing on two approaches: reference measurement and dual measurement. It addresses the challenge of applying UPV to curved surfaces, a scenario less studied than that of flat surfaces. The paper details the modification of UPV methodologies to account for curvature, presenting analytic solutions and numerical validations for both approaches. The findings reveal that curvature-adjusted equations yield accurate crack depth estimations, enhancing the reliability of UPV in diverse structural contexts. The study contributes to safer and more effective structural health monitoring, particularly in cylindrical infrastructures like columns and foundations. [ABSTRACT FROM AUTHOR]

The use of reinforced concrete is foundational to modern infrastructure. Acknowledging this, it is imperative that health monitoring techniques be in place to study corrosion within these structures. By using a non-destructive method for detecting the early formation of cracks within reinforced concrete, the method presented in this paper seeks to improve upon traditional techniques of monitoring corrosion, within reinforced concrete structures. In this paper, the authors present a method to evaluate the physical characteristics of reinforced concrete subject to corrosion using a poro-elastic acoustic model inversion technique applied to a set of ultrasonic measurements, which constitutes a novel approach to the problem of observing the impact of corroding rebars and resulting concrete damage. A non-contact ultrasonic transducer is operated at a carrier frequency of 500 [kHz], with a layer of saltwater separating the sensor from the concrete surface. Following this non-contact measurement collection of the surface and rebar echo responses, a poro-elastic model is used to model the sound propagation, through an adapted version of the Biot-Stoll model. At first, a set of default parameters, obtained from the physical characteristics of the reinforced concrete, are used to match experimental and simulated acoustic signature of the sample. Performing statistical averaging along the corroding rebar within three samples over a period of nearly nine months, a small but monotonous increase in the distance between the concrete surface and the top of the rebar, indicating gradual corrosion of the rebar. Next, a non-linear optimization algorithm is used to optimize the match between measured and simulated echoes. Through the implementation of this model parameter optimization, the root mean square error between measured and simulated responses was reduced by 63.7% for the full signal, and 62.6% for the rebar echo. [ABSTRACT FROM AUTHOR]

With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR's capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material's complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced. [ABSTRACT FROM AUTHOR]

Seismic methods will be useful for future lunar near‐surface characterization, and high‐fidelity elastic models will be required to aid interpretation of seismic observations. To develop an elastic lunar near‐surface model, we performed ultrasonic velocity measurements of lunar regolith simulant at low confining pressure and developed a rock physics model calibrated to these measurements. Grain contact models based on Hertz‐Mindlin theory produce accurate results at high confining pressure (i.e., several hundred meters or more burial depth) but historically fail to predict observed velocities in unconsolidated media at low pressure. Therefore, we heuristically modified existing models to fit our measured data over a range of porosities and confining pressures. To compare with Apollo 14 and 16 active seismic experiments, we used our new heuristic rock physics model to produce lunar subsurface velocity profiles. We performed ray tracing through our velocity profiles to calculate seismic traveltime, which results in good agreement with first arrivals interpreted from the Apollo experiments. Our model suggests a slightly higher velocity‐pressure dependence than inferred from in situ measurements, which may be due to porosity reduction in the lunar regolith from impact‐induced and natural vibrations. Plain Language Summary: Seismic velocity is the speed at which mechanical waves travel through planetary materials and is controlled by the physical properties of those materials such as density and compressibility. We have created a model that relates seismic velocity to depth and porosity under lunar conditions and have calibrated that model with laboratory measurements of lunar soil simulant at low pressure (i.e., near‐surface) conditions. Using this model, we can predict seismic velocity in the lunar subsurface and compare the modeled velocity with observations from Apollo active seismic experiments. Slight differences between our model and Apollo observations may be due to lower porosity in the lunar soil caused by vibrations from asteroid impact events and seismic quakes. Key Points: We collected ultrasonic velocity measurements of lunar regolith simulant at low confining pressure to calibrate a rock physics modelOur rock physics model predicts shallow lunar seismic velocity in agreement with observations from the Apollo active seismic experimentsOur model may be used in future studies to predict lunar near‐surface seismic velocity under variable resource scenarios [ABSTRACT FROM AUTHOR]

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Though previous studies have shown that the presence of water strongly influences wave responses of rock fractures, water effects on wave behaviours across clay-rich rock fractures have been ambiguous until now. In the present study, we conducted considerable ultrasonic measurements on single rock fractures filled with kaolinite-dominant gouges at varying water saturation degrees to investigate the water effects on elastic S-wave propagation and attenuation across clay-rich rock fractures. The experimental results reveal that the S-wave velocity across single clay-rich rock fractures slightly increases and decreases with the progressively increasing water saturation degree. An increase in water saturation leads to a concave trend of the spectral amplitudes, while it moderately affects the central frequency of transmitted S-waves. In addition, the seismic quality factor across single clay-rich rock fractures follows an exponential growth trend with the water saturation, suggesting the exponentially negative relation between S-wave attenuation and the water saturation. We attribute the water saturation-dependent S-wave attributes across single clay-rich rock fractures to the combined effects of the local flow and the degradation of grain contacts. Compared to P-wave, S-wave exhibits less sensitivity to varying water saturation of clay-rich rock fracture. Upon increasing water saturation, S-waves display similar velocity and central frequency trends with P-waves. The tendencies of spectral amplitude and seismic quality factor for S-waves are approximately opposite to those for P-waves as the water saturation degree increases. We interpret these discrepancies by the fact that S-wave attributes across single water-saturated clay-rich rock fractures mainly depend on the properties of the skeletal frame, while the characteristics of the particles, pore fluid, and skeleton frame dominate P-wave behaviours. The outcomes of the current work facilitate our understanding of the fluid effects on the interaction of waves with clay-rich rock discontinuities. Highlights: S-wave velocity and peak spectral amplitude across single clay-rich rock fractures exhibit concave trends upon rising water saturation. The increased water saturation modestly affects the central frequency of S-wave propagating across single clay-rich rock fractures. The seismic quality factor for S-waves exponentially grows with the water saturation degree of clay-rich rock fractures. The higher the S-wave frequency, the higher the wave velocity, the less the wave energy transmission, and the more the wave dissipation. The water-induced evolution of peak spectral amplitude and seismic quality factor for S-waves is roughly opposite to that for P-waves. [ABSTRACT FROM AUTHOR]

Understanding the quantitative responses of anisotropic dynamic properties in organic-rich shale with different kerogen content (KC) is of great significance in hydrocarbon exploration and development. Conducting controlled experiments with a single variable is challenging for natural shales due to their high variations in components, diagenesis conditions, or pore fluid. We employed the hot-pressing technique to construct 11 well-controlled artificial shale with varying KC. These artificial shale samples were successive machined into prismatic shape for ultrasonic measurements along different directions. Observations revealed bedding perpendicular P-wave velocities are more sensitive to the increasing KC than bedding paralleling velocities due to the preferential alignments of kerogen. All elastic stiffnesses except C13 are generally decreasing with the increasing KC, the variation of C11 and C33 on kerogen content are more sensitive than those of C44 and C66. Apparent dynamic mechanical parameters (n and E) were found to have linear correlation with the true ones from complete anisotropic equations independent of KC, which hold value towards the interpretation of well logs consistently across formations. Anisotropic mechanical parameters (DE and brittleness DB) tend to decrease with the reducing KC, with DB showing great sensitivity to KC variations. In the range of low KC (<10%), the VP/VS ratio demonstrated a linearly negative correlation with KC, and the VP/VS ratio magnitude of less than 1.75 may serve as a significant characterization for highly organic-rich (>10%) shale, compilation of data from natural organic rich-shales globally verified the similar systematic relationships that can be empirically used to predict the fraction of KC in shales. [ABSTRACT FROM AUTHOR]

The principle of reflection of ultrasonic waves at lubricated interfaces has been widely studied in recent years using different models. In this work, two different models (the spring model and the resonance model) were used to verify the influence of the acoustic properties of four different lubricating oils. A simple three-layer configuration was used, where carefully prepared, well-controlled gaps between stainless steel plates were established to accommodate a drop of oil. Optical measurements showed that the gaps formed were: gap 1 = 11 µm, gap 2 = 85 µm, gap 3 = 100 µm, and gap 4 = 170 µm. The smaller gap (11 µm) was found to be in the limit measurement range using the spring model for the sensor used in this work (14 MHz), whereas the resonance method was used for the thicker gaps. For the resonance model, the use of the phase spectra helped the identification of the resonance frequencies. The results showed good agreement between the measured thicknesses and the nominal gap values. There was little effect of the acoustic properties of the oils on the measured values, with the largest discrepancies found for the oil with the highest speed of sound (PAO4). This new way to characterize oil properties in a thin gap, where the material and geometry of the contact are fully characterized, enables us to compare different measurement methods and understand their sensitivity when testing similar materials of the same class of lubricants, as small deviations are crucial in real-life applications. [ABSTRACT FROM AUTHOR]